Within packaging technology where a packaging container is formed from a packaging material, it is known to provide the packaging material as a web which prior or during packaging is formed to the packaging container. Guiding marks, e.g. for optical reading has been provided to guide operations when finishing the package, such as forming, sealing, folding, etc. Such guiding marks are sometimes referred to as register marks. The register mark for optical reading is provided during printing of the packing material, where e.g. decoration or product information is printed on the packaging material. A problem with such register marks is that they consume a non-negligible area of what becomes the exterior of the package. A further problem is that such a register mark has to rely on the printing being well aligned with other operations performed on the web. It is therefore a desire to provide an improved provision of marking of web of packaging material.